The present invention relates to a special effect system for a television video signal, and particularly to a special effect system which produces special effects in which a video image is bent or turned, rolled up or is waved with reference to a designated reference straight line.
In a special effect system for a television video signal, various special effects are generated by storing a digital video signal in a memory and by producing special write or read address sequences which impart to the video signal a desired special effect. To obtain such special addresses, a function generating circuit in which a multiplier, a divider, an adder and a subtracter are combined is conventionally used. The resulting circuit is extremely complicated. Particularly, in order to generate effects in which the video image is turned, rolled up or waved with reference to the designated reference straight line, a trigonometric function and a hyperbolic function need to be generated. Conventionally, many multipliers, dividers, adders and subtracters are required for generating such functions and for modifying the generated functions. The combination thereof must be changed at times, thus resulting in a disadvantageous complicated configuration.
In order to overcome the aforementioned disadvantages, a new special effect system has been proposed in U.S. patent application Ser. No. 131,900 filed Dec. 11, 1987 and entitled "SPECIAL EFFECT SYSTEM FOR VIDEO SIGNAL". In the proposed system, one straight line is set up on a TV screen and a distance between the position of any given picture element and the straight line is calculated. In response to the calculated distance, a readable function memory delivers effective parameters to read out video data from a video memory so as to produce a special video effect. The proposed system has a relatively simple circuit configuration for producing special video effects.
However, the proposed system has the disadvantage that the turned and rolled-up effect images appear flat, i.e. two dimensional. In other words, turned and rolled-up images are not perceivable by a viewer to be three dimensional even though such effect images are oriented three-dimensionally.